The present invention relates to a new and improved construction of an automatic adjustment for a friction brake comprising at least two braking or brake elements between which there is arranged a brake lining, and which are pressed into contact with one another in a braking position.
Adjustment devices for friction brakes serve the purpose of compensating the increased size of the braking gap which is produced as a result of wear of the brake lining, so that such braking gap can be maintained approximately constant.
The heretofore known adjustment apparatuses, as a general rule possess adjustment elements which limit the air path or stroke either in a force-locking or form-locking manner.
The drawbacks of adjustment apparatuses working with a force-locking or frictional connection, generally reside in the fact that they are oftentimes much too complicated and expensive in construction. Also, for certain fields of application they fail to satisfactorily comply with the safety requirements imposed upon friction brakes, since due to wear or fabrication errors, unintentional displacements of the adjustment elements can arise.
These drawbacks are avoided with adjustment apparatuses of the second mentioned type. According to the construction of a self-adjusting jaw brake, as disclosed in U.S. Pat. No. 3,710,897, the connection rod of the brake levers carrying the brake jaws, is provided at one end with a conical portion or tapered socket of large diameter, upon which there are arranged to suspend in vertical direction, thin plate-shaped adjustment elements. The adjustment elements possess keyhole-shaped openings, and they are guided upon the conical portion by means of the circular-portion of the opening. Upon decrease of the spacing between both brake levers, due to wear of the brake lining on the order of magnitude amounting to the thickness of an adjustment element, the connection rod shifts by the same amount relative to the adjustment elements. The adjustment element suspended at the beginning of the conical portion therefore slides down and falls onto the connection rod, and is guided by means of the slot-portion of the keyhole thereon. Consequently, the decrease of the spacing between both brake levers, resulting from wear, cannot be eliminated since the connection rod is blocked in a form-locking manner by means of the adjustment element which has slid down.
The drawback of this adjustment apparatus particularly resides in the fact that the movement of the adjustment elements is accomplished by the force of gravity, so that it is dependent upon position and cannot be used for all applications. Since the positive functioning requires the use of sufficiently heavy adjustment elements, such must possess a minimum thickness, with the result that the adjustment, under some circumstances, becomes much too coarse.